Newbie looking at solar install in Fremont, CA

[J.P.M.]

I did some research on tilt and it seems that optimal tilt changes throughout the year but I don't find it practical to manually adjust tilt. So, I plan to just set fixed tilt if my roof pitch is too flat. I plan to have most panels south facing but I have less south facing roof space so I may need to have more west facing panels. Regarding inverters, I was planning on micro-inverters. Would that make it easier to have panels facing different directions than string inverters you mentioned? Thanks.

Optimal tilt does change as the earth's declination changes. Decent 1st approx. for year round perf. for fixed tilt is to tilt to local latitude if facing south, a bit higher but not much, if a little off south, and higher tilt the farther off south you get. A few PVWatts runs will usually zero it in fairly well.

[inetdog]

I did some research on tilt and it seems that optimal tilt changes throughout the year but I don't find it practical to manually adjust tilt. So, I plan to just set fixed tilt if my roof pitch is too flat. I plan to have most panels south facing but I have less south facing roof space so I may need to have more west facing panels. Regarding inverters, I was planning on micro-inverters. Would that make it easier to have panels facing different directions than string inverters you mentioned? Thanks.

Yes, and you do not need to have the same number of panels in each string.
West facing strings, depending on local weather and shading conditions, may be almost as good as South facing strings. And for Grid Tie they have the advantage of more production during peak rate hours. Although TOU pricing is going through some major changes that reduce the payback on even West facing panels.

[bcroe]

Regarding inverters, I was planning on micro-inverters. Would that make it
easier to have panels facing different directions than string inverters you mentioned? Thanks.

If you use strings, all the panels in each string should have the same orientation. No such restriction
with micro-inverters. Bruce Roe

[solardreamer]

For my part, you're welcome.

The tilt (angle of the array(s)) with the horizontal is pretty important. Not quite as crucial as azimuth, but important to get correct. If arrays are going to be mounted parallel to the roof they sit on, use the roof azimuth and slope. Also remember, you can split arrays - some panels south, some west, etc. just remember that not all string inverters can handle multiple orientations or strings of varying sizes. Read the help/info screens.

I did some research on tilt and it seems that optimal tilt changes throughout the year but I don't find it practical to manually adjust tilt. So, I plan to just set fixed tilt if my roof pitch is too flat. I plan to have most panels south facing but I have less south facing roof space so I may need to have more west facing panels. Regarding inverters, I was planning on micro-inverters. Would that make it easier to have panels facing different directions than string inverters you mentioned? Thanks.

[bcroe]

As long as partial shading is not an issue, any single MPPT input can handle two identical length
strings in different orientations with little loss over putting the two strings on independent MPPT inputs.

That is what is happening here. 5 equal length strings connected to an inverter; 3 facing south,
one facing east, and one facing west. They work well together, even the one facing away from
the sun is able to generate some power. Bruce Roe

[inetdog]

... just remember that not all string inverters can handle multiple orientations or strings of varying sizes. Read the help/info screens.

As long as partial shading is not an issue, any single MPPT input can handle two identical length strings in different orientations with little loss over putting the two strings on independent MPPT inputs.
Different length strings, no way unless they do not produce at the same time.

But the trend these days is for string inverters to offer at least two MPPT inputs.

[J.P.M.]

Thanks for the info. It took a while to figure it all out but based on PVWatts hourly output data for south and west facing installations and my PG&E TOU rate plan (EV-A) it seems that south facing installation is clearly better than west facing installation for my location. Based on what I have read, I am a bit surprised the results were not closer. One thing I am not sure about is the tilt parameter in PVWatts. I just used the default value (20).

For my part, you're welcome.

The tilt (angle of the array(s)) with the horizontal is pretty important. Not quite as crucial as azimuth, but important to get correct. If arrays are going to be mounted parallel to the roof they sit on, use the roof azimuth and slope. Also remember, you can split arrays - some panels south, some west, etc. just remember that not all string inverters can handle multiple orientations or strings of varying sizes. Read the help/info screens.

[solardreamer]

Run PVWatts and remember that the 14% default may be a bit conservative. Use the hourly output option and search for clear day outputs for an ESTIMATE of MAX. prod. at various times of the year.

Thanks for the info. It took a while to figure it all out but based on PVWatts hourly output data for south and west facing installations and my PG&E TOU rate plan (EV-A) it seems that south facing installation is clearly better than west facing installation for my location. Based on what I have read, I am a bit surprised the results were not closer. One thing I am not sure about is the tilt parameter in PVWatts. I just used the default value (20).

[bcroe]

Thanks for the info. I see you installed the panels facing south but I heard that facing west would be best for maximizing net metering credit. Did you consider west facing installation?

If you have ground mounted panels, there are lots of options possible. Roof mount or significant
shading will force designing the system around these limitations. Keep reading old & new posts,
tons of info here. My panels face 3 directions. Bruce Roe

[J.P.M.]

Thanks for the info. I see you installed the panels facing south but I heard that facing west would be best for maximizing net metering credit. Did you consider west facing installation?

The best orientation for T.O.U. to maximize revenue is probably not as absolute as south or west, but somewhere between those two depending on location sunshine availability and weather as well as use patterns. Since most roofs are fixed, an alternative is to split the # panels, probably unevenly, some on west facing roof with the rest on the south facing roof. Often, putting more/most on the south roof will result in the most $$ bang. Facing due west of an entire array is probably not the best $$ return for most locations.

[solardreamer]

No problem. System has been up for year and a few days. A panel got changed, so the DC rating is 4100W in total panels. Roof is facing south. I got 7300 KWh in the first year. According to the NREL estimator, with a 14% derate factor, I was supposed to get 6500 or 6600 KWh in the first year. Mind you, we're in the middle of a drought with few rainy days. So, I'm guessing that this is as good as it'd get for annual production. Net net, I'm happy, I covered about 90% of my production and won't get charged anything with time of use pricing.

Thanks for the info. I see you installed the panels facing south but I heard that facing west would be best for maximizing net metering credit. Did you consider west facing installation?

[JCP]

I am also in Fremont considering solar and was wondering if you could share some info about your solar system. You indicated your 4 kw-DC system is generating 29 kwh per day. Is this DC kwh? And is it higher or lower compared your original plan? What is your average daily DC kwh over the last year? I am trying to size system to avoid significant over-production. I am wondering if the general guideline of using 5 sun hours per day for Fremont is really valid. You seem to be getting much more than 5 sun hours per day. Also, do you know your actual derate factor for DC-to-AC conversion? The NREL guideline is 77% but that seems very conservative. I believe you are using Enphase micro-inverters which supposedly have higher derate factor but I wonder what is the real-world performance.

Any info would be appreciated. Thanks.

No problem. System has been up for year and a few days. A panel got changed, so the DC rating is 4100W in total panels. Roof is facing south. I got 7300 KWh in the first year. According to the NREL estimator, with a 14% derate factor, I was supposed to get 6500 or 6600 KWh in the first year. Mind you, we're in the middle of a drought with few rainy days. So, I'm guessing that this is as good as it'd get for annual production. Net net, I'm happy, I covered about 90% of my production and won't get charged anything with time of use pricing.

[J.P.M.]

I am also in Fremont considering solar and was wondering if you could share some info about your solar system. You indicated your 4 kw-DC system is generating 29 kwh per day. Is this DC kwh? And is it higher or lower compared your original plan? What is your average daily DC kwh over the last year? I am trying to size system to avoid significant over-production. I am wondering if the general guideline of using 5 sun hours per day for Fremont is really valid. You seem to be getting much more than 5 sun hours per day. Also, do you know your actual derate factor for DC-to-AC conversion? The NREL guideline is 77% but that seems very conservative. I believe you are using Enphase micro-inverters which supposedly have higher derate factor but I wonder what is the real-world performance.

Any info would be appreciated. Thanks.

Run PVWatts and remember that the 14% default may be a bit conservative. Use the hourly output option and search for clear day outputs for an ESTIMATE of MAX. prod. at various times of the year.

[solardreamer]

System has been installed. Last stop is getting the net metering agreement from PG&E. The 4080 DC watts systems currently cranks out 29 KWh a day. Happy camper.

I am also in Fremont considering solar and was wondering if you could share some info about your solar system. You indicated your 4 kw-DC system is generating 29 kwh per day. Is this DC kwh? And is it higher or lower compared your original plan? What is your average daily DC kwh over the last year? I am trying to size system to avoid significant over-production. I am wondering if the general guideline of using 5 sun hours per day for Fremont is really valid. You seem to be getting much more than 5 sun hours per day. Also, do you know your actual derate factor for DC-to-AC conversion? The NREL guideline is 77% but that seems very conservative. I believe you are using Enphase micro-inverters which supposedly have higher derate factor but I wonder what is the real-world performance.

Any info would be appreciated. Thanks.

[JCP]

Congrats! Have you fired it up yet? How long did PG&E take to give you the approval? I'm finishing up my self-installed system now and will be sending in the Net Metering agreement as soon as the inspector signs it off, hopefully in about a week. Just curious how long PG&E is taking.

My installer did all the paperwork, so I really don't know how long the whole process took. Actual dates: final install, system turned on 5/18. PGE net metering started 6/26. Right now, I'm building a nice cushion since my production exceeds my consumption. Obviously, that'll change in a few months.